One big reason why Google’s profit grew more slowly than its revenue was a higher tax rate: 18% in the first quarter, compared with 9% in the same quarter last year. Google CFO Patrick Pichette told investors the higher rate reflects the expiration of the research-and-development tax credit at the end of last year.

Other big tech companies use the credit. Among those that reported first-quarter results this week, Intel, Yahoo and IBM all saw their effective tax rates increase this year compared with last year’s first quarter, though none of them appeared to call out the expired tax credit as a reason.

In an analysis last year, the Journal found that the extension of the tax credit in January 2013 reduced tech companies’ reported income-tax expenses in the first quarter of 2013 by hundreds of millions of dollars.

In Google’s case, the higher tax rate meant per-share earnings of $5.33. If Google had paid tax at last year’s rate, earnings would have been $5.93.

It’s not clear that the research credit fully explains the jump in Google’s tax rate; it increased only marginally from the fourth quarter.

First enacted in 1981, the research credit has expired eight previous times. Each time, it ultimately was renewed, with companies allowed to claim the credit retroactively. The latest expiration was Dec. 31, 2013, and Congress has yet to renew it.